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BQ27621-G1: Unexpected SOC occurs after setting registers

AMB
Prodigy 100 points
Part Number: BQ27621-G1
Other Parts Discussed in Thread: GPCCHEM, BQSTUDIO

Hi,

Can you support on following

I am using 900mAh, 3330mWh battery. So accordingly I set Design Capacity and Design Energy. I want 0 percentage at 3.1V so I set terminate Voltage to 3100. and Taper rate to 12 as continuous current flow from my device is 735mA. 

I am using Quick Start Guide flow-chart and TRM.

But I do not get expected result of SOC I have also tried with charging battery fully to 4.2V.

I am getting SOC 50percent at 3Volt. If I don't charge the battery fully lets say stops charging at 3.7V and then run the code I do get 100 percent SOC. Which is very much unexpected.

I am not getting why this behavior.

  • 0
    TI__Mastermind 27321 points

    Hello, 

    Did you follow section 3.2 for Procedure to Select Alternate Chemistry? Make sure you are using correct battery chemistry profile. 

    If you are not sure about the battery chemistry you are using, please use our GPCCHEM tool to find if your battery is well matched to one of the three supported chemistries.


    These are the chemistries this gauge support. The result from the GPCCHEM tool will tell you if it matches to one of these three. 


    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 100 points

    Hi Jose,

    We are using linux platform hence we unable to use BQStudio and GPCCHEM tool.

    I tried using alternate chemistry but still seeing random jump of SOC.

    I am getting

     

    And direct jump to 

    And direct jump to 

    I do not want this jumping behavior.

    I am using battery of 4.2V maximum charge voltage so I do not see reason to change the chemistry.

    Can you suggest any other things. Because now i am seeing this Battery Gauge is not gauging properly.

  • 0 in reply to AMB
    TI__Mastermind 27321 points

    Hello AMB,

    Choosing alternate chemistries will not fix the SOC jump. This is voltage correlation gauge, meaning that if the cell chemistry OCV table differs from the programmed ChemID OCV lookup table, the SOC will be inaccurate. 

    I suggest to use the GPCCHEM tool, this one will report if your battery chemistry is close enough to ChemID 1202 which is 4.2V based.

    Also, do you have the smooth enable feature ON? I would disable RCJUMPOK and enable SMTHEN


    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 100 points

    Hi,

    SMTHEN is enable by default.

    Does the gauging issue resolved by using tool?

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    The tool will verify if the proper ChemID is programmed on the gauge. Our suspicion is that the incorrect ChemID is programmed on the gauge which is why you are seeing this issue.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Hi,

    We do not have I2C to USB to use that tool. But I have set ChemID to default and also try with remaining two ChemIDs but I do not see good response. Kindly find attached logs for SOC. It is very much unexpected behavior.  

    Do you have any other solution?

    Fullscreen battery_log_TI_Charging.txt Download 
    Voltage: 3.393000
SOC: 100
Voltage: 3.440000
SOC: 100
Voltage: 3.466000
SOC: 100
Voltage: 3.489000
SOC: 100
Voltage: 3.544000
SOC: 100
Voltage: 3.540000
SOC: 100
Voltage: 3.554000
SOC: 100
Voltage: 3.568000
SOC: 100
Voltage: 3.595000
SOC: 100
Voltage: 3.610000
SOC: 100
Voltage: 3.621000
SOC: 100
Voltage: 3.664000
SOC: 100
Voltage: 3.652000
SOC: 100
Voltage: 3.664000
SOC: 100
Voltage: 3.675000
SOC: 100
Voltage: 3.690000
SOC: 100
Voltage: 3.700000
SOC: 100
Voltage: 3.711000
SOC: 100
Voltage: 3.749000
SOC: 100
Voltage: 3.733000
SOC: 100
Voltage: 3.743000
SOC: 100
Voltage: 3.742000
SOC: 100
Voltage: 3.763000
SOC: 100
Voltage: 3.769000
SOC: 100
Voltage: 3.775000
SOC: 100
Voltage: 3.798000
SOC: 100
Voltage: 3.781000
SOC: 100
Voltage: 3.781000
SOC: 100
Voltage: 3.782000
SOC: 100
Voltage: 3.781000
SOC: 100
Voltage: 3.784000
SOC: 100
Voltage: 3.784000
SOC: 100
Voltage: 3.805000
SOC: 100
Voltage: 3.813000
SOC: 100
Voltage: 3.814000
SOC: 100
Voltage: 3.815000
SOC: 100
Voltage: 3.813000
SOC: 100
Voltage: 3.818000
SOC: 100
Voltage: 3.818000
SOC: 100
Voltage: 3.838000
SOC: 100
Voltage: 3.822000
SOC: 100
Voltage: 3.822000
SOC: 100
Voltage: 3.823000
SOC: 100
Voltage: 3.846000
SOC: 100
Voltage: 3.827000
SOC: 100
Voltage: 3.829000
SOC: 100
Voltage: 3.824000
SOC: 100
Voltage: 3.833000
SOC: 100
Voltage: 3.834000
SOC: 100
Voltage: 3.836000
SOC: 100
Voltage: 3.859000
SOC: 100
Voltage: 3.841000
SOC: 100
Voltage: 3.843000
SOC: 100
Voltage: 3.840000
SOC: 100
Voltage: 3.847000
SOC: 100
Voltage: 3.849000
SOC: 100
Voltage: 3.850000
SOC: 100
Voltage: 3.873000
SOC: 100
Voltage: 3.856000
SOC: 100
Voltage: 3.857000
SOC: 100
Voltage: 3.853000
SOC: 100
Voltage: 3.862000
SOC: 100
Voltage: 3.863000
SOC: 100
Voltage: 3.865000
SOC: 100
Voltage: 3.885000
SOC: 100
Voltage: 3.868000
SOC: 100
Voltage: 3.870000
SOC: 100
    Fullscreen battery_log_TI_Discharge.txt Download 
    Voltage: 3.795000
SOC: 100
Voltage: 3.466000
SOC: 100
Voltage: 3.449000
SOC: 100
Voltage: 3.418000
SOC: 100
Voltage: 3.441000
SOC: 98
Voltage: 3.436000
SOC: 96
Voltage: 3.428000
SOC: 95
Voltage: 3.370000
SOC: 93
Voltage: 3.371000
SOC: 92
Voltage: 3.295000
SOC: 90
Voltage: 3.246000
SOC: 88
Voltage: 3.163000
SOC: 85
Voltage: 3.044000
SOC: 0
Voltage: 2.895000
SOC: 0

  • 0 in reply to Adrian
    Prodigy 100 points

    Hi Nick,

    I just came to know about ChemID

    .

    Our ChemID is 1254. And from BQ27621 datasheet only three chemistry is supported. 

    What we have to do for our chemistry?

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    ChemID 1202 will most likely be the best match. What is interesting is that you have tried test on all three ChemIDs with no success. Can you send a data  dump of all the parameters for the gauge. I want to see if there is something not configured correctly. Can you also send me the datasheet for your battery?

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Yes sure.

    Kindly find below screenshot for the data dump on the gauge registers and also attached datasheet of battery.

    DNK-LP502470 3.7V 1000mAh datasheet-Ver.1.0.pdf

    Let me know if anything wrong 

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hello AMB,

    Everything looks fine. I want to revisit checking the GPCCHEM tool to verify that all 3 chemIDs are not compatiable (which is what I am suspecting is the case since you are not seeing good results with any 3 of the ChemIDs). You do not need BQStudio to use the GPCCHEM tool. All you need to do is log time, voltage, current, and temperature.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Hi,

    I have seen improvements in charging log after changing jumper of BIN to Low.

    Below is the connections of BQ27621 Eval. Can you please check and confirm if everything is ok?

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hello AMB,

    Yes, I believe the connections look good.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Thanks Nick,

    Can you tell me how to enable interrupt of 1percent change in SOC.

    I believe the default settings are enabling above but i wont be able to receive 1ms pulses on GPOUT pin.

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    Section 2.5.1 of the TRM talks about this.

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Hi,

    Yes I gone through this. The default settings are okay to generate the interrupt I want. i.e OPconfig BatLowEn  is cleared.

    But I am not receiving interrupt on GPOUT pin.

    GPIOPOL kept to active Low and gave external pull up to Vdd.

    Can you please confirm the hardware changes, GPIOPOL and pull ups and other necessary 

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    The hardware changes seem correct. What is your test setup that you are using to capture the interrupt pulse from GPOUT pin?

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    I just connect DSO probe on GPOUT pin to check whether i am getting interrupt pulse or not

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    Thank you for confirming your test setup. This is a problem I haven't personally seen before, so I will need to consult with some other members on my team regarding this.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Hey Nick,

    Any updates?

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    I should be able to give you an update next week.

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    Prodigy 100 points

    Hi Nick,

    Thank you I got the solution. After connecting GPOUT pin to the controller GPIO pin I could able to resolve the issue.

    Thank you so much for your support

  • 0 in reply to AMB
    TI__Mastermind 37761 points

    Hey AMB,

    That is great to hear. Glad I was able to lead you in the right direction.

    Regards,

    Nick Richards